A circuit board having a conductive paste layer for connecting to a conductive pattern formed on a surface of an insulation substrate is disclosed, for example, in Japanese Patent Application Publication No. H06-140788. The circuit board includes a substrate as the insulation substrate, a copper pattern as the conductive pattern, an under coat layer as a lower insulation layer, a conductor as a shield layer and an over coat layer as an upper insulation layer, which are laminated in this order. The copper pattern is disposed on the surface of the substrate. The lower insulation layer covers the copper pattern. The copper pattern is exposed from the lower insulation layer through a contact hole so that the copper pattern electrically contacts the conductor. The upper insulation layer covers whole of the conductor, the lower insulation layer and the copper pattern completely.
Therefore, in the circuit board, it is difficult to evaluate the characteristics of the conductor. Further, it is difficult to determine whether the circuit board having the conductor has good performance.